1. Field of the Invention
The present invention relates to a multilayer ceramic capacitor.
2. Description of the Related Art
In recent years, in order for multilayer ceramic capacitor to miniaturize, obtain larger capacitance, reduce cost and obtain higher reliability, internal dielectric layer which is arranged between 2 internal electrode layers facing each other, is making progress to become thinner. Concretely, thickness of an internal dielectric layer after firing is made thinner to around 1 μm. As the thickness of an internal dielectric layer is made thinner, volume ratio of internal electrode layers made up in capacitor device body (tip sintered body) become larger.
Conventionally, dielectric material for additives is added to internal electrode layer paste forming internal electrode layer in order to restrain breaking by firing, sintering of base metal conductive materials such as Ni, etc. (see Japanese Patent Publication (A) No. 5-62855, Japanese Patent Publication (A) No. 2000-277369, Japanese Patent Publication (A) No. 2001-307939, Japanese Patent Publication (A) No. 2003-77761 and Japanese Patent Publication (A) No. 2003-100544). Dielectric material for additives added to the internal electrode layer paste is diffused to the internal dielectric layer during firing the non-fired capacitor device body. Therefore, as dielectric material for additives added to the internal electrode layer paste increases, diffusing ratio to internal dielectric layer during firing becomes higher.
Namely, in recent years, as internal dielectric layers become thinner and number of stacked layer increases, volume ratio of internal electrode layer paste pattern made up in capacitor device body before firing become large. Compared to the case without making internal dielectric layer thinner, during firing, the ratio of dielectric material for additives diffused in internal dielectric layer is becoming higher.
Consequently, particle growth of dielectric particles composing internal dielectric Layer were urged and the microstructure of internal dielectric layer were affected. With this effect to the microstructure, all kinds of electric characteristics (tan δ, bias characteristic, temperature characteristic, reliability) of obtained multilayer ceramic capacitor may have been deteriorated.
Japanese Patent Publication (A) No. 2003-133164 discloses multilayer ceramic capacitor wherein the average particle size of dielectric particles near external electrodes is equal to or smaller to that of dielectric particles in the executive area. However, the object of the technical as in Japanese Patent Publication (A) No. 2003-133164 is to prevent crack at external electrode when sintering.